When 4 layers & 2 layers transmission is used with 8x8 config

RAN
1

Hello Experts.

Considering:

DL closed-loop MIMO Transmission (4 layers): to verify that gNB supports closed-loop DL single user 4 layers transmission with 4T4R or 8T8R configuration

DL closed-loop MIMO Transmission (2 layers): to verify that gNB supports closed-loop DL single user 2 layers transmission with 4T4R or 8T8R configuration

Like here UE is reporting RI, PMI to eNB & based on that precoding is performed at TX side or eNB side, as per quote we can see when we have 4x4 config, we have 4 layers here.

So can any please help to understand, when we will be having 8x8 config, is 8 layers are the most desirable MIMO?

Also when 4 layers & 2 layers transmission is used with 8x8 config?

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2

Almost there is no any device which supports 8×8 and maximum is 4×4 just 8×8 or higher helps for better rank.

3

Ok thanks!

So you mean to say even if we configure 8 TXRX at eNB & we took a device with 4 TXRX, we can get 4 layers max (but 8x8 MIMO config is not available as of now for real UEs)?

4

Yes, just 8×8 helps UE get more rank 4.

5

Ok.

Thanks, so below is my understandings on MIMO layers, correct me if anything looks wrong to you…

So we have left with two options:

8 TXRX at eNB side & 4 TXRX at UE side → 4 layers will be applicable
8 TXRX at eNB side & 2 TXRX at UE side → 2 layers will be applicable

More TXRX in eNB side configured means it helps to get better RI & so enabling better MIMO to get better throughput .

We have closed loop MIMO when UE are in static good RF position (TM4 will be used here)

We have open loop MIMO when UE are in high mobility (TM3 will be used here)

6

Yes, correct.